Pump



Oct. 14, H. N. WYLE PUIIP Filed Aug. 2, 1944 4 SheetsSheet 1 Oct. 14,1947' H.IN. WYLIE v 5 PUMP Filed Aug. 2, 1944 4 sheets-sheet s 44 v Q 0J5 J5 J7 C) M Q E J /5 /8 O 42 5 /4 40 4/ A5 56 Z O 0 f7 J /9 r O fyefl/ ki i 12mm 21 Aw Hi)? H. N. WYLIE Oct. 14, 1947.

PUMP

Filed Aug. 2, 1944 4 Sheets-Sheet 4- Ja e/ 7 A MM W 1 Patented Oct. 14,1947 Hamilton Neil Wylie, London,

England, assignor toAircraft Hydraulic Appliances Limited, London,England Application August 2,

In Great Britain 14 Claims. (Cl. 103-461) There is a known type of pumpwhich comprises a cylinder assembly mounted to be driven for rotation ona valve shaft having lands to define an inlet leading to the cylindersand an outlet from them, the cylinders being directed radially orsubstantially radially, and pistons in the cylinders which areconstrained to reciprocate therein by a track ring, usually of circularform. The track ring is movable between various positions in which it iseccentric with reference to the aXis of rotation of the cylinderassembly, or between concentric and eccentric positions, so that thestroke of the pistons, and consequently the rate of delivery of the pumpfor given running speeds, is variable. The track ring is loaded towardsan eccentric position by controlling means in opposition to which fluidpressure produced in the cylinder assembly in operation of the pumpagainst pressure actsto reduce eccentricity of the track ring, therebyreducingv the effective stroke of the pistons, and correspondingly theoutput.

In United States Patent 2,293,692 there was disclosed an extremelyimportant improvement in such pumps of that general type above stated,the improvement residing in the feature that the track ring was urgedtowards its position of maximum eccentricity by resilient means (e. g.,a spring), and the pump reaction, which is of course the total reactionof the pistons on the track ring, due to the internal pressure built-upin the pump when it is acting against pressure at the pump outlet-asfully explained in the aforesaid specification No. 2,293,692-was madeeffective to urge the track ring towards its position of minimumeccentricity in opposition to the resilient means. The arrangement wassuch that not the total reaction force but only a component of the totalreaction force operated in opposition to the resilient means loading thetrack ring to its position of maximum eccentricity.

It is to the general type of pump first hereinbefore described, butmodified in such a way that only a component of the total reaction forceoperates in opposition to the resilient means loading the track ring toits position of maximum eccentricity, that the present inventionessentially relates, and for convenience in the following descriptionsuch a pump is designated a pump of the type hereinbefore specified.

It has been found that when the track ring is mounted to be movable byrocking, the said critical pressure is effected by the viscosity of thefluid dealt with by the pump, and this has been found to be caused bythe viscous drag between 1944, Serial No. 547,750

1 as described in the prior ferred that each piston August 10, 1943 therotating cylinder assembly and the ring ap- I plying a rocking force tothe track ring in opposition to the component of the total reactionforce, which, in conjunction with the resilient means, determine thesaid critical pressure.

The objectof the present invention is to provide structural meanssupporting the track ring which oppose forces tending to rotate or rockthe ring while giving it freedom to move to change its eccentricity.

In preferred embodiments of the invention, the pump rotor (that is tosay the rotating cylinderand-piston assembly) rotating in the pumpcasing acts as an impeller to centrifuge working fluid delivered to theinterior of the pump from an inlet relatively near the axis of rotationof the rotor to an outlet relatively remote from the axis, from whichoutlet of the centrifuge stage a branch communicates with the inlet tothe cylinder assembly, through which working fluid is delivered to thecylinders at an initially boosted pressure.

United States specification 2,293,693; the centrifuge. stage being alsoutilised (as described therein, to discharge through an outlet branch)to circulate fluid through an external cooling circuit.

In regard to the bearing means which operate between the pistons and thetrack ring, it is preshall have a slipper-bearing surface rockablysupported by or pivotally connected to the piston for slidablecooperation with the track ring to operate on the principle of Michellpad bearings.

It is to be appreciated that although the slipper bearings arepreferred, other suitable bearings may be provided. Likewise it followsthat, although in the preferred embodiments the pump operates with acentrifuge stage, there may be cases in which the centrifuge stage isunnecessary.

Referring to the drawings- Figure 1 is a side elevation of a pumpaccording to the invention looking coaxially and showing the inlet andoutlet ports;

Figure 2 is a section on ure 1; while Figure 3 is a section on the lineIII-I1I of Figure 2; and

Figure 4 is a sectional view illustrating a modification.

Referring now to the accompanying diagrammatic drawings, of which Figure3 is possibly the most important from the point of view of illustratingthe invention, the pump casing is represented by the reference numeralN. The track the line 11- of Figring is of circular form and isrepresented by the reference numeral l I. The valve shaft I2 is suit-lably borne in the casing and embodies the-inlet or suction duct l3 andthe outlet or pressure duct I4. The valve lands l5 and f6 serve todefine .ports ll and IB. The rotor assembly is constitutcd by a centralrotor body part, represented generally by the reference numeral IS, inwhich radial cylinders 20 are formed. The rotor body incorporates ahubportion 2| at one end, which is drivably connected with the splineddrive coupling 22 suitably borne for rotation in the casing. A piston 23operates in each cylinder 20 and mounts at its outer end theslipper-:bearing member 24, which conveniently can be pivotallyconnected to the piston by the wrist-pin 25. The bearing slippers 24operate as Michell pad bearings, so that they virtually run on a fiim ofoil interposed between the outer bearing surface of the slippers and theinner periphery of the track ring H. The stroke of the pistons 23 in thecyl inders 20 of course depends on the eccentricity of the track ring,so that when the track ring is disposed concentrically the pistons haveno stroke; but when the track ring is eccentric in relation to the valveshaft, the cylinders as they pass the stationary port I I take in fluidas their volume increases, assuming clockwise rotation of the rotor; andas the volume is reduced again, due to the rotor eccentricity, thecylinders discharge the fluid they have taken in on the suction strokeinto the port [8, from which it passes away to the outlet through theoutlet or pressure duct M.

In regard to the-manner in which working fluid is delivered to and fromthe valve shaft, the inlet to the pump is seen at 26 in Figure 1. Theinlet feeds into the interior of the pump within the track ring. Innormal rotation the rotor centrifuges liquid through the slot 21 of thetrack ring into the centrifuge chamber 28, from which the duct 29 runsinward to duct 13 and inlet port I1 and into the cylinders, from whichit is forced by the pistons 23 into the outlet port l8, and

thence into the high-pressure system. Any instantaneous excess pressureseeps past relief valve 3|, through holes 32A and 32B into thecentrifuge outlet 32.

The centrifuge stage is preferably capable of delivering more fluid thanis required to supply the cylinders, and the excess escapes through bore13A and holes 32A and 32B and out through the centrifuge connection 32,and thus forms a cooling circuit.

The track ring I l is loaded to its fully-eccentric position, as shownin Figure 3, by the control force exerted by the spring 33 when thetotal reaction force (represented in Figure 3 by the arrow R) is notsufliciently large to reduce the stroke.

As so far described, the pump according to the present inventionoperates in the same manner as that described in the aforesaid UnitedStates specification No. 2293,692; but it will be appreciated that incertain cases, for instance when the pump is utilised to provide thesource of pressure for a hydraulic system of an aircraft which may becalled upon to operate under extremely low temperatures at highaltitude, the oil or other fluid of the system may become very viscous.In that event the viscous drag as between the bearing surface of theslippers 24 and the track ring I I can resolve itself into a turningmoment operating about the track ring centre, thereby tending to causethe track ring to hinge or rock, in the direction in which it is urgedby the spring 33; and if that rocking or hinging tendency is notcounteracted, it causes an increase in pumping pressure which may beexcessive. The present invention is therefore directed essentially tothe actual mounting of the track ring H.

It will be appreciated that since the total reaction force on the ringhas only a small component parallel to the direction in which the ringmoves, the means used for mounting the ring must be of a kind to movewith very little friction.

A flattened portion 35 is provided on the track ring between which and ab-aring p.ate 36 roller bearings 31 operate. The rollers 31 are mountedin a cage 38, which moves in the same direction as the ring and throughhalf the distance. The rollers are held against slipping between theflat surfaces by the load imposed by the pistons on the ring except whenthe pump is not generating pressure, and the ring then must be atmaximum eccentricity. In this condition the cage 38 is located by thespring 39 pressing it against the pin 4|, which is fixed to the ring andmoves in a slot 40 in the cage 38. The pin 42 projects into the slot 40to assist in guiding and locating the cage 38. i

It will be appreciated that the drag moment could affect theeccentricity of the ring only if the track ring were permitted to rockabout one of the rollers, and such rocking action is prevented by therollers being spaced adequately apart. The reaction force R passesbetween the rollers close to the one remote from the spring 39, and thering is therefore firmly held against this roller against the turningmoment due to viscous drag which tends to lift it from the roller androck it about the roller adjacent the spring 39.

The casing includes a pad or seating 34 opposite the rollers 3'! whichprevents the ring from dropping out of place when the pump is notdeveloping pressure.

In the pump shown in Figures 1 to 3, the spring 33 is of laminated leafform, mounted inside the casing In, with one end located at 43 and theother end free to slide on the casing. The small rod 44 is interposedbetween the track ring H and a point of the spring 33 intermediate itsends. The spring 33 is considerably deflected when the ring is atmaximum eccentricity, and the deflection, and hence the force it exerts,increases as the eccentricity decreases. The pressure characteristicsdepend among other things on the ratio between the deflection imposed onthe spring at no eccentricity and that imposed at maximum eccentricity.Conveniently, the position of track ring maximum eccentricity is definedby the segment 45. When the reaction moment builds up at the criticalpressure, a slight additional rise causes the ring it to move over inopposition to the spring 33 until delivery is reduced to zero. i I

For the spring 33 operating as the resilient means for loading the trackring to its maximum eccentricity position, any other suitable form ofresilient control might be substituted. Thus, a spiral spring might behoused in the casing between the track ring and a suitable fixedabutment, which might be adjustable. Generally speaking, however, theleaf type of spring is preferable because it can be conveniently fittedinto the casing. In all preferred constructions the spring 33 is oflaminated form, the several laminae preferab y being stopped atgraduated distances from the free end of the spring, as is usual on leafsprings to provide adequate flexibility; but all the laminae extend tothe located 'sure at which the pump will end of the spring and are thereclamped together in any suitable manner, thus giving an increase indamping effect. The use of a laminated spring of the constructiondescribed and clearly seen at 33 in Figure 3 provides for a markeddamping effect on variation of deflection, which is advantageous in somecases. Moreover, such a spring provides a convenient means of initialadjustment of the rate of the spring because the rate can be increasedas the spacer rod 44 is moved towards the fixed anchorage end 43. Theactual force exerted ,by the spring 33 can be varied at choice oninstallation by selection of any one of several differently-dimensionedspacer rods 44.

Spacer rod 44 can be located in any convenient manner; for instance itmay be engaged in lateralIy-spaced metal strips one at each side of thespring 33 and secured at the fixed anchorage 43 in any suitable manner.

The pump characteristics and the critical presangular setting of the bevaried on installation is dependent upon the valve shaft, which can todirect the reaction force Generally speaking, the characteristics .willbe determined on assembly of the pump; and having determ'ned the finalsetting of the valve shaft it is locked against rotation with respect tothe casing by means of the dowel 41, seen in Figure 1. There may becases, however, in'which provision is made for adjustment of the valveshaft l2.

Itris convenient to utilize the specially-formed segments 45 and 46inside the casing I as the stop means for limiting the'range of movementof the track ring, but any other convenient stop means may be provided,and in certain cases such alternative stop means, provided for in stanceby bolts extending through the casing I0, may be operable externally oradjust the limit positions of the track ring.

An alternative construction in which the track ring is supported on inFigure 4, in which the relevant parts similar to those shown in Figure.3 are designated by the same reference numbers.

The track ring II, which is acted on by the reaction force R, issupported by a tension link 50 pivoted to the block secured to thecasing l0, and by a block 52 secured to the track ring I I, the trackring being also supported by a compression link 53 resting in a groovedblock 54 secured to the casing l0, and awblock 55 secured to the trackring. Parts I l, 50 and 53 are shown in full lines in the position ofmaximum eccentricity and in broken lines in the position of noeccentricity. A bending strut- 56 abutting against block 51 securedblock 58 secured to the track ring ll provides the resilient meansforcing the track ring towards the position of maximum eccentricity, anda pad 34 is arranged to support the track ring when the pump isdeveloping no pressure and prevents the block 55 from falling clear oflink 53.

The arrangement is preferably such that the links are parallel when thetrack ring is in its mean position, and the links may be of equallength, in which case the track ring will be a straight The tension linkmay be shorter pression link. in which case the block 52 will be pulleddown towards each end of the range more than the block 55 is permittedtorise; hence the centre of the ring will be pulled down slightly line,

R appropriately.

pivoted links is illustrated to the casing I0 and than the com react inoperation the casing to the path'of the centre of I towards each end ofthe range, thus doing work against the force R which acts upwards. iswould give rise to forces urging the ring from maximum eccentricitytowards the central or mean position, and also from minimum eccentricity. The effect of this on the ring is the same as would result frommaking the strut 56 exert an increasedforce at small stroke and adecreased force at full stroke, and this in certain cases is a desirableeffect. a

If thecornpression strut were shorter than the tension strut, theopposite efiect would result, and this might also be desired in certaincases.

If both links were tension links, the effect would be that due to a longcompression link and short tension link, only more so, and if both linkswere struts, the effect would be that of a long tension link and a shortcompression link, but more so.

The arrangement can be used in conjunction with the leaf spring 33illustrated in Figure 3 to compensate for the diminishing force exertedby the spring as the eccentricity increases, or in conjunction with thealternative spiral spring housed in the casing referred to on page 9, inwhich the spring acts between the track ring and a suitable fixedabutment, which may be a the hollow boss in the casing which containsthe sprin What I claim is: v

1. In a pump including a track ring, a radial type piston and cylinderassemblyv mounted for rotation in said ring, and means mounting saidring for movement from a position of maximum eccentricity to a positionof minimum eccentricity relative to the center of said assembly, themagnitude of the eccentricity of said ring determining the stroke of thepistons of said assembly; the reaction forces incident to operation ofthe pump tending to bias the ring to its position of minimumeccentricity; resilient means biasing said ring toward the position ofmaximum eccenits positions of eccentricity and thereby preventingmodification of the load imposed on said resilient means by the reactionforces acting on the ring when the pump is in operation.

2. 'In a pump including a track ring, a radial type piston and cylinderassembly mounted for rotation in said ring, and means supporting saidring for movement from a position of maximum eccentricity to a positionof minimum eccentricity relative to the center of said assembly, themagnitude of the eccentricity of said ring determining the stroke of thepistons of said assembly; the reaction forces incident to operation ofthe pump tending to bias the ring to its position of minimumeccentricity; resilient means biasing said ring toward the position ofmaximum eccentricity against the reaction forces acting on the ring whenthe pump is in operation, and means intermediate said ringand said ringsupporting I type piston and cylinder assembly mounted for rotation insaid ring, and means supporting said ring for movement from a positionof maximum plug screwed into and said ring supporting I means foropposing rotation of the ring in all of path between saidposieccentricity to a position of minimum eccentricity relative to thecenter of said assembly, the magnitude of the eccentricity of said ringdetermining the stroke of the pistons of said assembly, reaction forcesincident to operation of the pump tending to bias the ring to itsposition of minimum eccentricity; resilient means biasing said ringtoward the position of maximum eccentricity against the reaction forcesacting on the ring when the pump is in operation, and axially rotatablebearing members situated on one side of the track ring between it andsaid supporting means, said bearing members lying on opposite sides of aline representing the reaction force which presses the ring onto themwhen the pump is developing pressure whereby, angular rocking movementof the track ring due to viscous drag between the piston and cylinderassembly and. the track ring is prevented.

4. A pump as claimed in claim 3 wherein a portion of the ring supportingmeans is provided with a fiat surface and a portion of the ring is alsoprovided with a flat surface between which fiat surfaces the axiallyrotatable bearing members are interposed,

5. A pump as claimed in claim 3 wherein the track ring is provided witha flat surface and the ring supporting means is also provided with aflat surface, said axially rotatable bearing members being interposedbetween said flat surfaces and which further comprises a cage withinwhich said axially rotatable bearing members are mounted, a projectionextending from the fiat surface of said ring, and spring means urgingthe cage against said projection when said ring is in its position ofmaximum eccentricity.

6. In a pump including a track ring, a radial type piston and cylinderassembly mounted for rotating in said ring, and means supporting saidring for movement from a position of maximum eccentricity to a positionof minimum eccentricity relative to the center of said assembly, themagnitude of the eccentricity of said ring determining the stroke of thepiston of said assembly; the

reaction forces incident to operation of the pump tending to bias thering to its position of minimum eccentricity; resilient means biasingsaid ring toward the position of maximum eccentricity against thereaction forces acting on the ring when the pump is in operation, andspaced link members extending between said ring and said ring supportingmeans, said link members bein constructed and arranged to opposerotation of the ring while permitting the ring to move to change itseccentricity.

7. A pump as claimed in claim 6 wherein one of the link members is atension link and the other member is a compression link and wherein thelinks are parallel with one another in the mean position of the trackring.

8. A pump as claimed in claim 6 wherein the link members are arranged onopposite sides of the track ring and on opposite sides of a linerepresenting the reaction forces acting on the ring when the pump is inoperation.

9. A pump as claimed in claim 6 wherein the link members are of equallength.

10. A pump as claimed in claim 6 wherein the link members are of unequallength.

11. A pump as claimed in claim 6 wherein both link members are tensionlinks.

12. A pump as claimed in claim 6 wherein both link members arecompression links.

13. A pump as claimed in claim 6 wherein one of the link members is atension link and the other link member is a compression link and whereinthe two links are of equal length.

14. A pump as claimed in claim 6 wherein the resilient means comprises abending strut.

HAMILTON NEIL WYLIE.

REFERENCES CITED UNITED STATES PATENTS Name Date Wylie Aug. 18, 1942Number

